The more quickly you walk, the faster the calories burn. A 140-pound woman burns about four calories a minute if she walks a mile in 20 minutes (or 3 miles per hour). The calories jump to 5.2 per minute for a 15-minute mile (4 mph) or 7.7 per minute for a 12-minute mile (5 mph).

Walking is an equal opportunity exercise, says Kathy Smith, a fitness instructor who created a walking program exclusively for us. "There aren't any biases against uncoordinated people, and everyone knows how to do it. It's a 'no excuses workout' because you don't need equipment or a gym."

You don't even have to walk outside to get health benefits. A treadmill burns more calories and raises cardiovascular fitness more effectively than stationary bikes, stair climbers, rowers, and ski machines, according to a 1996 study by the Medical College of Wisconsin and Veterans Affairs Medical Center in Milwaukee. Why? The researchers believe that people work harder while walking because it's something they do every day.

Don't move an inch until you've got shoes made for walking. They should have good arch support, fairly low but well-cushioned heels, and good flexibility at the ball of the foot, says Mark Fenton, a five-time member of the U.S. National Racewalking Team and coauthor of The 90-Day Fitness Walking Program.

Try on shoes in the afternoon, when your feet are largest, with the type of socks you'll wear while walking. Choose shoes that don't slip at the heel, and leave a thumbnail's width between your big toe and the shoe's tip. For rough trails, you'll do better in a high-cut light hiking or rugged walking shoe.

Replace your walking shoes at least every six months or after walking 500 miles, whichever comes first, Fenton says. Make a note on your calendar, because "even if they look fine at the end of six months, the cushioning loses its ability to absorb the impact. One of the best ways to hurt yourself is to wear old shoes," he says. Like many walkers, Fenton alternates two pairs -- a new one and an older one. "When you start looking forward to wearing the new ones, you know it's time to retire the old ones."

Veteran walkers know that socks should be made of a cotton blend to avoid any blister-causing dampness. Also, fight the heat by wearing a hat, sunscreen, sunglasses, and light colors to reflect the sun.

The right technique prevents
fitness-walking injuries.

You know how to walk, but do you know the best way to walk? Stand up straight, keep your chin parallel to the ground, and move with a sense of purpose. Your ears should be directly over your shoulders, hips, knees, and feet. Arms should swing freely, and when you want to pick up the pace, bend your elbows to an 85-degree angle and keep them close to your body. Your hands should never rise above mid-chest level or fall past your hips, says Smith. "Your arms are like pistons -- boom, boom."

To really work, lean your entire body slightly forward as if a rope is around your chest pulling you. Your steps move in closer, with one foot in front of the other as if you were walking a tightrope. But stick to the same pace.

To help keep your head up, scan the path by looking 15 feet ahead and lowering your eyes, not your chin. Keep your hands free by wearing your portable radio, heart monitor, or water bottle on a hip belt. Skip leg and hand weights, which throw off your gait and could hurt your back and shoulders.

Strive to exert yourself at a level 6 on a scale of 1 to 10, with 0 being very relaxed and 10 being your maximum output. You should be able to talk, but not be able to sing, says Smith. "If you're panting, you're working too hard."

Drink 8 ounces of water an hour before you start walking, then another 4 to 5 ounces just before you start, says Martin Yadrick, a registered dietitian and sports nutritionist in Los Angeles. To determine how much fluid you need to replace after exercising, weigh yourself before and after. For every pound lost, you should drink 16 ounces.

If you find you're losing steam, focus on the next mailbox you pass or on reaching the end of the song you're listening to. Or, entertain yourself with music. It not only helps pass the time but boosts your energy, according to a recent study conducted at Springfield College in Springfield, Massachusetts.

If you ever want to see how far you're walking, measure your route with your car's odometer.

Don't walk alone outdoors after dusk, and keep one ear free to hear traffic if you're listening to music.

To avoid injury, you'll want to increase the length of your walks by no more than 10 to 20 percent from week to week.